The Propeller

Probably the most important parts of an airplane, after the wing, are the propeller and engine. The propeller (or, on jet aircraft, the jets) provides the thrust that moves the plane forward. (Check out How Gas Turbine Engines Work to learn about jet engines.)

A propeller is really just a special, spinning wing. If you looked at the cross section of a propeller, you'd find that a propeller has an airfoil shape and an angle of attack. Just by looking at the propeller pictured above, you can see that the angle of attack changes along the length of the propeller -- the angle is greater toward the center because the speed of the propeller through the air is slower close to the hub. Many larger propeller aircraft have more elaborate three-blade or four-blade props with adjustable pitch mechanisms. These mechanisms let the pilot adjust the propeller's angle of attack depending on air speed and altitude.